New laser technologies in ophthalmology for normalisation of intraocular pressure and correction of refraction

Baum, Olga I.; Yuzhakov, Alexey V.; Bol'shunov, A V; Siplivy, V. I.; Khomchik, O.V.; Zheltov, G. I.; Sobol, Emil N.

doi:10.1070/qel16368

Cited by 15 publications

(11 citation statements)

References 4 publications

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“…Unlike irradiation by a Gaussian beam used here and previously in , panel (B) corresponds to the irradiation performed with a ring‐shape, wider beam that produces a smoother distribution of temperature profile more adequate for cornea reshaping in problems of eye refraction correction. The power density was close to that in and test experiments described below, in which the irradiation intensity was ~30% higher than the optimal level deduced from data …”

Section: Structural Changes In Collagenoues Tissues Produced By Modersupporting

confidence: 83%

Revealing structural modifications in thermomechanical reshaping of collagenous tissues using optical coherence elastography

Zaitsev

Matveyev

Matveev

et al. 2018

Journal of Biophotonics

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Moderate heating of such collagenous tissues as cornea and cartilages by infra‐red laser (IR laser) irradiation is an emerging technology for nondestructive modification of the tissue shape and microstructure for a variety of applications in ophthalmology, otolaryngology and so on. Postirradiation high‐resolution microscopic examination indicates the appearance of microscopic either spheroidal or crack‐like narrow pores depending on the tissue type and irradiation regime. Such examinations usually require special tissue preparation (eg, staining, drying that affect microstructure themselves) and are mostly suitable for studying individual pores, whereas evaluation of their averaged parameters, especially in situ, is challenging. Here, we demonstrate the ability of optical coherence tomography (OCT) to visualize areas of pore initiation and evaluate their averaged properties by combining visualization of residual irradiation‐induced tissue dilatation and evaluation of the accompanying Young‐modulus reduction by OCT‐based compressional elastography. We show that the averaged OCT‐based data obtained in situ fairly well agree with the microscopic examination results. The results obtained develop the basis for effective and safe applications of novel nondestructive laser technologies of tissue modification in clinical practice. PICTURE: Elastographic OCT‐based images of an excised rabbit eye cornea subjected to thermomechanical laser‐assisted reshaping. Central panel shows resultant cumulative dilatation in cornea after moderate (~45‐50°C) pulse‐periodic heating by an IR laser together with distribution of the inverse Young modulus 1/E before (left) and after (right) IR irradiation. Significant modulus decrease in the center of irradiated region is caused by initiated micropores. Their parameters can be extracted by analyzing the elastographic images.

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Section: Structural Changes In Collagenoues Tissues Produced By Modersupporting

confidence: 83%

Revealing structural modifications in thermomechanical reshaping of collagenous tissues using optical coherence elastography

Zaitsev

Matveyev

Matveev

et al. 2018

Journal of Biophotonics

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“…The expressions for the radial and angular components of the thermal stress tensor were obtained in the analytical form by solving the thermoelasticity equations assuming cylindrical symmetry of the temperature field T ( r )created by the heating laser beam. Then, under laser irradiation of a tissue layer by laser beam with cylindrical symmetry, the resultant thermal stress (described by the difference between the angular and radial component of the thermal stress tensor) can be written in the following form convenient for numerical integration, which we used earlier in works :

σ_{therm} = italicαE ((), - normalΔ T ((), r) + \frac{2}{r^{2}} \int_{0}^{r} normalΔ T ((), r') r' italicdr')

where α is the coefficient of thermal expansion, E is the Young modulus and Δ T ( r ) is the temperature increase from the background value. Taking into account that for biological tissues with Poisson's ratio close to 0.5, the Young modulus E is related to shear modulus G as E = 3 G and the nomalized temperture increase can be written as

normalΔ \overset{T}{true} ((), r) = normalΔ T ((), r) / normalΔ T ((), r = 0)

.…”

Section: Methodsmentioning

confidence: 99%

“…Laser treatment of tissues is a rapidly developing field of biophotonics and medical physics in general. Biologically, nondestructive laser‐induced modification of several types of collagenous tissues, such as cartilaginous tissue , sclera and cornea, is a perspective branch of this field. For example, the laser‐induced temperature and thermal‐stress fields allow for changing the cartilaginous sample shape, which can be used for manufacturing allo‐ and autoimplants.…”

Section: Introductionmentioning

confidence: 99%

Interplay of temperature, thermal‐stresses and strains in laser‐assisted modification of collagenous tissues: Speckle‐contrast and OCT‐based studies

Baum

Zaitsev

Yuzhakov

et al. 2019

Journal of Biophotonics

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Moderate heating of collagenous tissues such as cartilage and cornea by infrared laser irradiation can produce biologically nondestructive structural rearrangements and relaxation of internal stresses resulting in the tissue reshaping. The reshaping results and eventual changes in optical and biological properties of the tissue strongly depend on the laser‐irradiation regime. Here, a speckle‐contrast technique based on monochromatic illumination of the tissue in combination with strain mapping by means of optical coherence elastography (OCE) is applied to reveal the interplay between the temperature and thermal stress fields producing tissue modifications. The speckle‐based technique ensured en face visualization of cross correlation and contrast of speckle images, with evolving proportions between contributions of temperature increase and thermal‐stresses determined by temperature gradients. The speckle‐technique findings are corroborated by quantitative OCE‐based depth‐resolved imaging of irradiation‐induced strain‐evolution. The revealed relationships can be used for real‐time control of the reshaping procedures (e.g., for laser shaping of cartilaginous implants in otolaryngology and maxillofacial surgery) and optimization of the laser‐irradiation regimes to ensure the desired reshaping using lower and biologically safer temperatures. The figure of waterfall OCE‐image demonstrates how the strain‐rate maximum arising in the heating‐beam center gradually splits and drifts towards the zones of maximal thermal stresses located at the temperature‐profile slopes.

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“…Using a laser helps changing the conformation of collagen molecules located on the periphery of the cornea and in the limb. The method uses a special header that creates a circular distribution of the intensity of laser radiation [8][9][10][11], that allows us to achieve a more uniform effect of the weakening of mechanical stresses and leads to a reduction in laser-induced complications, since symmetric with respect to the paracentral zone cornea, but sequential irradiation of a number of points can lead to asymmetry of the corneal tension in the optical zone and the occurrence of astigmatism, keratoconus and other complications [8]. In addition, research is being carried out in the direction of developing a control system that allows one to determine the threshold for the onset of stress relaxation in the corneal tissues during laser irradiation.…”

Section: Introductionmentioning

confidence: 99%

Study of Laser Radiation Effect on the Cornea of the Eye by Speckle Interferometry

Fedulova

Yuzhakov

Baum

2020

J-BPE

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The existing techniques of laser vision correctionone of the most widespread operationsare based presently on a surgical intervention in cornea tissue. Our science team is engaged in studying of in essence new type of correction based on a modification of structure and the field of mechanical tension of a cornea. In this work, the possibility to use of a speckle interferometry method as a basis for the tracking system of cornea structural changes at thermal influence of a nondestructive laser radiation is considered. Also for a cornea, the polymeric phantom was picked up.

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New laser technologies in ophthalmology for normalisation of intraocular pressure and correction of refraction

Cited by 15 publications

References 4 publications

Revealing structural modifications in thermomechanical reshaping of collagenous tissues using optical coherence elastography

Revealing structural modifications in thermomechanical reshaping of collagenous tissues using optical coherence elastography

Interplay of temperature, thermal‐stresses and strains in laser‐assisted modification of collagenous tissues: Speckle‐contrast and OCT‐based studies

Study of Laser Radiation Effect on the Cornea of the Eye by Speckle Interferometry

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